This invention relates to an improved portable adsorber which specifically can treat fumes at point sources generated from procedures and equipment and which can capture fumes emanating from the point source which are both lighter-than-air and heavier-than-air, thereby preventing such fumes from migrating into the room in which the point source is located.
Histopathology and graphic arts are two of many areas where this portable adsorber would protect the artisan from the toxic fumes used in their work. In histopathology, the laboratory technician in routine procedures allows OSHA (Occupational Safety Health Administration) regulated solvents to escape into the laboratory environment. By simply opening the tissue specimen container, where the tissue is routinely preserved in formalin (an aqueous solution of formaldehyde), formaldehyde gas is allowed to escape into the room environment. Recent findings by the CIIT (Chemical Industry Institute of Toxicology) that experimental testing with rats exposed to formaldehyde resulted in squamous cell carcinomas and the Consumer Products Safety Committee's ban on urea-formaldehyde insulation bring forward the prospect that formaldehyde could be classified as a cancer-suspect agent which causes concern in the medical area because of formaldehyde's prevalent use. Similarly xylene and alcohol, both OSHA regulated substances are used extensively in staining and coverslipping slides in the medical area.
Similarly, an artist uses hazardous solvents to dissolve and mix with oil, resins, varnishes and inks and to remove paint, dyes, varnish and lacquers from brushes, tools and hands. In addition to the inhalation effects of these solvents (drowsiness), these solvents are flammable and serious incidents have occurred. The artist and histologist have to be able to perform their craft with minimum interference to their ability to use the hands and eyes and this invention affords that opportunity with a large measure of protection for the artisan.
Normal protection in the medical laboratory is afforded by working in a laboratory hood where sufficient velocity is maintained to capture the solvent and exhaust the fume into the outside environment. To achieve the high capture velocity (150 feet per minute) required in the hood, the sash is frequently closed to reduce the hood opening and thus obtain the high capture velocity required. Since large ventilation systems, to which a laboratory hood is connected, required frequent balancing which has become even more critical with the universality of air conditioning; often fumes exhausted from one laboratory hood are re-introduced unintentionally into another part of the ventilation system instead of outdoors. The EPA (Environmental Protection Agency) requires treatment of carcinogen and regulates the introduction of organic emissions into the ambient environment.
To reduce the large loss of energy involved in providing the capture velocity required to exhaust the fumes and to treat fumes at their source of generation prior to dilution, fume adsorbers which enclose the procedure or equipment have been developed (U.S. Pat. No. 4,276,819). Fume adsorbers are deficient in that they are small to achieve a measure of portability yet require a balance between adsorbent depth and capture velocity to achieve treatment and yet prevent fume escape. Fume adsorbers do not achieve the capture velocities of laboratory hoods and result in reduction of visual and hand manipulation ability.
By way of background, to provide protection during welding U.S. Pat. No. 3,818,817 describes a flexible duct supported on a floating arm connected to a permanently mounted blower which exhausts particulate fumes external to the building. A large amount of room energy is lost in this pollution control method. U.S. Pat. No. 3,926,104 describes a welding pollution control system where particulates are treated by electrostatic means and the treated air can be recirculated back into the room. Flexibility of this treatment system is reduced since the local exhaust hood and electrostatic treatment unit have to be positioned over the work. All situations where it could be used dictate that a large open overhead space be available over the fume generating source. U.S. Pat. No. 4,318,337 describes a special molded fiberglass local exhaust hood to increase the capture of the welding fumes. The described mounting appears less flexible than the floating arm/duct arrangement. The treatment techniques described in U.S. Pat. No. 4,318,337 involve electrostatic precipitation and solvent recovery which are both large systems not lending themselves to portability. U.S. Pat. Nos. 3,913,470 and 3,380,371 describe large exhaust systems with unique manifolding to locate the local exhaust hood over the fume generating source.
In addition, there are situations where the noxious fumes and vapors which are emitted from a point source are both lighter-than-air and heavier-than-air. Thus, prior point source adsorbers in which the fume-capturing duct was located above the point source could only capture the lighter fumes while permitting the heavier fumes to migrate downwardly.